containers from scratch - in rust

Minimal re-implementation of lizrice/containers-from-scratch in Rust.

why?

Liz Rice gave several fantastic talks at DockerCon and other events named Containers from Scratch. In these talks, she impressively live-codes a minimal container runtime in about 100 lines of Golang.

Many important container tools such as docker/engine, opencontainers/runc, etc are written in Golang. Golang is a great tool for building and running containers and I love the language. However, safely handling syscalls in the language can sometimes be tricky. Rust offers a safe, memory-efficient and memory-safe wrapper around the syscall C-bindings and enforces strict error handling. Due to these safety improvements, I believe Rust is a good choice to reimplement Liz Rice's cfs example. Also, I'm trying to find any excuse to write Rust!

In this repository, I've attempted to write a very minimal container runtime, based Liz Rice's original Golang implementation.

Note: I'm pretty new to Rust and this is not idiomatic code. If you have any suggestions, please send a PR or ping me on Discord!

Credit:

• vas-quod for examples and snippets on how to use the nix package.
• Liz Rice's Containers from Scratch talk
  • note: to see her Golang implementation, see lizrice/containers-from-scratch

usage

This will only work on a Unix system. I developed in WSL2.

# build the Docker container
make build

# run a shell
make run

# run args in the mini-container!
cfs args...

examples

How do you know this is working?

example 0: new hostname

# run hostname in the Docker container
root@e8f49cd2ff70:/home# hostname
e8f49cd2ff70

# run hostname in the cfs container: we've changed hostnames
root@e8f49cd2ff70:/home# cfs run hostname
cfs-container

example 1: isolated process view

# run ps in the container
root@cb3e7658f63f:/usr/src/cfs# ps
  PID TTY          TIME CMD
    1 pts/0    00:00:00 sh
    7 pts/0    00:00:00 bash
    8 pts/0    00:00:00 ps

# run ps in cfs: the container thinks cfs is PID 1
root@cb3e7658f63f:/home# cfs run ps
  PID TTY          TIME CMD
    1 ?        00:00:00 cfs
    2 ?        00:00:00 ps

example 2: restricted view of mounts (still need to fill in output)

# run mount in the container
root@cb3e7658f63f:/home# cfs run mount